A communication system including a multi-function peripheral and a mobile terminal is known. When an application is activated by a user, the mobile terminal determines whether a device ID assigned from the multi-function peripheral is being stored, and operates in a P2P (abbreviation of Peer To Peer) mode of the NFC standard in a case of determining that the device ID is not being stored, and operates in a CE (abbreviation of Card Emulation) mode in a case of determining that the device ID is being stored. In a case where the mobile terminal operates in the P2P mode, the multi-function peripheral operates in the P2P mode, and sends the device ID to the mobile terminal by using an NFC communication. In a case where the mobile terminal operates in the CE mode, the multi-function peripheral operates in the R/W (abbreviation of Reader/Writer) mode, receives the device ID from the mobile terminal by using an NFC communication, and executes an authentication using the device ID.